Inkjet nozzle assembly having displaceable roof defining ejection port

1. An inkjet nozzle assembly comprising:

a nozzle chamber having a floor and a roof spaced apart from the floor, said roof having a displaceable portion defining an ejection port; and

an actuator for displacing the displaceable portion of the roof towards the floor,

wherein displacement of the displaceable portion of the roof alters a volume of the nozzle chamber such that when the volume is altered, fluid is ejected from the ejection port.

2. The inkjet nozzle assembly of claim 1 , wherein said actuator is a thermal bend actuator.

3. The inkjet nozzle assembly of claim 2 , wherein said thermal bend actuator comprises a first active beam arranged above a second passive beam.

4. The inkjet nozzle assembly of claim 3 , wherein said first active beam thermally expands relative to the second passive beam when a current flows through the first active beam.

5. The inkjet nozzle assembly of claim 1 , wherein an ink inlet is defined in the floor of the nozzle chamber.

6. A printhead comprising: a silicon substrate, a passivated CMOS layer disposed on the silicon substrate and a plurality of nozzle assemblies disposed on the passivated CMOS layer, each nozzle assembly comprising:

a nozzle chamber having a floor and a roof spaced apart from the floor, said roof having a displaceable portion defining an ejection port; and

an actuator for displacing the displaceable portion of the roof towards the floor,

wherein displacement of the displaceable portion of the roof alters a volume of the nozzle chamber such that when the volume is altered, fluid is ejected from the ejection port.

7. The printhead of claim 6 comprising a plurality of bond pads connected to the CMOS layer.

8. The printhead of claim 6 , wherein said nozzle assemblies are arranged in rows, said rows being grouped in pairs of offset nozzle rows, each pair being supplied with a common ink.